/*
自己选择的路 ,跪着也要走完。朋友们 , 虽然这个世界日益浮躁起来,只
要能够为了当时纯粹的梦想和感动坚持努力下去 , 不管其它人怎么样,我
们也能够保持自己的本色走下去。
To the world , you will be a person , but to a person , you
will be the world .                               ——AKPower
*/
// 作者 : AKPower
// 算法 :二分加二维前缀
#include <iostream>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <vector>
#include <map>
#include <queue>
#include <cstdio>
#include <string>
#include <stack>
#include <set>
#define IOS ios::sync_with_stdio(false), cin.tie(0)
using namespace std;
typedef long long ll;
const ll maxn = 110;
ll a[maxn][maxn], p[maxn][maxn];
ll n, m;

bool judge(ll mid)
{
    for (ll i = mid; i <= n; i++)
    {
        for (ll j = mid; j <= m; j++)
        {
            ll sum = p[i][j] - p[i - mid][j] - p[i][j - mid] + p[i - mid][j - mid];
            // cout << "mid = " << mid << endl;
            // cout << "sum = " << sum << endl;
            if (sum == mid * mid)
                return true;
        }
    }
    return false;
}

int main()
{
    IOS;
    cin >> n >> m;
    for (ll i = 1; i <= n; i++)
    {
        for (ll j = 1; j <= m; j++)
        {
            cin >> a[i][j];
            p[i][j] = p[i - 1][j] + p[i][j - 1] - p[i - 1][j - 1] + a[i][j];
            // cout << p[i][j] << endl;
        }
    }
    ll l = 0, r = min(n, m);
    ll mid;
    while (l <= r)
    {
        mid = (l + r) >> 1;
        if (judge(mid))
        {
            // cout << "mid = " << mid << endl;
            l = mid + 1;
        }
        else
            r = mid - 1;
    }
    cout << r << endl;
    getchar();
    getchar();
    return 0;
}
